The present invention relates to a system for controlling the timing of cylinder valves used in a reciprocating internal combustion engine. This system uses a very precise measure or indication of valve closing in combination with rotary position sensing of a camshaft or crankshaft.
With dual equal or dual independent operation of camshaft timing, the trapped air charge for a given intake manifold pressure is affected by the intake valve closing timing. For a V-type engine, differences in bank-to-bank cam timing will result in corresponding differences in air charge and indicated mean effective pressure (IMEP). Under conditions in which the camshaft timing is retarded significantly at part load, the negative effect on IMEP may cause significant noise, vibration, and harshness (NVH) if the bank-to-bank camshaft timing difference exceeds two crankshaft angle degrees. It has been found that the stack up of production level manufacturing and assembly tolerances may in certain cases exceed this limit. In one particular engine, the difference in bank-to-bank cam timing angle was expected to exceed twelve crankangle degrees. This variation would be expected to result in severe NVH problems.
A system and method according to present invention solves the problem of achieving precise control of camshaft timing by providing a marker which corresponds to the actual valve closing for at lease one valve for each bank of cylinders. This is achieved by measuring the structural load upon the camshaft, which provides a very clear and precise measurement of the valve spring force acting upon the camshaft, which is in itself an accurate indication of the actual valve position. This measurement may be employed in the control system feedback loop or as an adaptive update to current feedback systems which generally use signals from a trigger wheel and sensor. An alternative approach could be to employ a knock sensor to determine valve closing from the knock sensor output under conditions where closing could be reliably measured, such as during idle. The knock sensor measurement can be used for adaptively updating a trigger wheel or sensor system mounted on either a camshaft or the crankshaft.
A system for controlling the timing of a cylinder valve camshaft in a reciprocating internal combustion engine includes a camshaft structural force sensor for sensing structural force upon the camshaft, with said structural force being associated with a predetermined unique rotational position of the camshaft, and with the structural force sensor generating a camshaft event signal corresponding to said predetermined unique position. A camshaft timing sensor determines the rotational position of the camshaft and generates a rotary position signal corresponding to the rotational position of the camshaft. A controller receives the camshaft event signal and the rotary position signal. The controller comprises a comparator for comparing the position of the camshaft as indicated by the rotary position signal with the predetermined rotational position of the camshaft corresponding to the camshaft event signal. The controller may further comprise a corrector for correcting the rotary position signal based upon the results of the comparison. In one embodiment of the present invention, a camshaft structural force sensor may comprise a load washer associated with a bearing fastener of the camshaft. This load washer may, for example, comprise of piezoelectric force sensor mounted under a camshaft bearing fastener.
According to another aspect of the present invention, a controller receives a crankshaft position sensor position signal and a valve position signal. The controller comprises a predictor for predicting valve position based on the sensed position of the crankshaft, and a comparator for comparing at a predetermined crankshaft position, the actual poppet valve position as determined by the controller from the valve position signal, with the predicted valve position. The controller creates an error signal in the event that the difference between the actual poppet valve position and the predicted valve position exceeds a predetermined threshold.
According to yet another aspect of the present invention, a method for controlling the timing of a cylinder valve camshaft incorporated within a reciprocating internal combustion engine includes the steps of sensing the presence of a structural force upon the camshaft associated with a unique rotational position of the camshaft, reading the indicated rotational position of the camshaft by means of a camshaft position sensor when said structural force is sensed, comparing the unique rotational position of the camshaft, as evidenced by the presence of said structural force, with the indicated rotational position of the camshaft, and correcting the indicated rotational position of the camshaft in the event that the difference between the indicated camshaft position and the unique rotational position exceeds a predetermined threshold.
According to another aspect of the present invention, a system for controlling the timing of a poppet valve operating system in a reciprocating internal combustion engine includes a sensor for sensing a vibration associated with the closing of one or more poppet valves, and for generating a valve closing signal corresponding to the onset of said vibration. A timing sensor determines the rotational position of a rotating shaft that is in the engine and generates a rotary position signal corresponding to the rotational position of the shaft. Finally, a controller receives the valve closing signal and the rotary position signal and compares the value of the rotary position signal with the predetermined rotational position of the shaft corresponding to generation of the valve closing signal.
It is an advantage of the present invention that the xe2x80x9cdead-reckoningxe2x80x9d provided by conventional sensor wheels and pickups may be corrected by a very precise signal corresponding to the actual closing of a valve.
It is a further advantage of the present invention that a system according to this invention will allow more precise control of engine output torque and engine out feedgases.
It is a further advantage of the present invention that the system according to this invention will allow superior NVH performance of an engine.
Other advantages of the present invention as well as objects and features thereof will become apparent to the reader of this specification.